Various diseases and disorders can adversely affect an individual's neurological and/or cognitive function. For example, multiple sclerosis (MS) is a chronic, progressive disease of the central nervous system (CNS), in which the myelin sheaths of axons of the brain, spinal cord and optic nerve become damaged, resulting in an inflammatory response. MS can lead to demyelination and scarring, as well as a broad spectrum of signs and symptoms, which often progresses to physical and cognitive disability.
MS-related disability ranges from minimal to severe, and evolution of disease manifestations over time is variable—both in the specific nature of the symptoms and disability and in the rate of deterioration. The historical approach to measuring MS-related disability has been use of a neurologist rating scale, called the Kurtzke Expanded Disability Scale (EDSS). The EDSS rates disease severity using a 20 point scale, ranging from 0 to 10 in 0.5 point increments, with increasing numbers reflecting increased disability. However, the EDSS has been criticized because it is neither precise nor quantitative. A newer approach has been to evaluate MS disease severity using a 3-part composite, called the Multiple Sclerosis Functional Composite (MSFC). The MSFC is a three-part, standardized, quantitative, assessment instrument for use in clinical studies, particularly clinical trials of MS. The MSFC can produce scores for each of the three individual measures—walking, arm function, and cognitive function—as well as a composite score. However, since the MSFC measures are administered in person by a trained examiner, its usefulness outside of clinical settings tends to be impaired.